Demonstration of Fourier transformation

The first file construct signals from Fourier terms
The second file analyzes actual signals

[ff,cc]=fourier2(SR,T)

function [ff,cc]=fourier2(SR,T)
%This file can acquire data from any signal voltage connected to the
%line-in port of the computer sound card (this should not exceed
%a peak value of one volt), perform fast Fourier transformation
%and produce plot and numerical data of the frequency spectrum
%of the signal.
%The input arguments are SR which is the signal sampling rate.
%This can be between 8000 and 44000, and the period of time T in seconds during which the signal is sampled it can range between 0.001 sec up to few seconds.
%The output data are the data ff, and cc used in plotting the frequency
%spectrum
ai=analoginput('winsound')
addchannel(ai,1:2);
ai.samplerate=SR;
ai.samplespertrigger=SR*T;
ai.triggertype='immediat';
start(ai);
[d,t]=getdata(ai);
N=length(t);
u1=d(:,1);
y=fft(u1,1024);
p=y.*conj(y);
c=(p.^(1/2));
ff=[1:1024]*N/(max(t)*1024);
cc=c/max(c);
plot(ff(1:512),cc(1:512))
grid
delete(ai)
clear ai